state standard 2e. compare the advantages of sexual reproduction and asexual reproduction in...

State Standard

2E. Compare the advantages of sexual reproduction and asexual reproduction in

different situations.

Meiosis & Sexual Reproduction (10.1)

Human body cells have 46 chromosomes

10.1 Meiosis

Sexual Reproduction and Genetics

Each parent contributes 23 chromosomes

Chapter 10

Homologous chromosomes—one of two paired chromosomes, one from each parent

Chromosomes & Chromosome Number

Chromosomes & Chromosome Number Cont’d10.1 Meiosis


Same length

Same centromere position

Carry genes that control the same inherited traits

Chapter 10

Homologous Chromosomes have…

These chromosomeshave replicated

These chromosomes Have not replicated

Haploid and Diploid Cells


Gametes are haploid. The contain half the normal # of chromosomes for the organism. (n)Human gametes = 23 chromosomes

All other body cells (aka somatic cells) are diploid. They contain the normal # of chromosomes for the organism. (2n)Human body cells = 46 chromosomes.

10.1 Meiosis

An organism produces gametes to maintain the same number of chromosomes from generation to generation.

Chapter 10

Meiosis Meiosis is a special

type of cell division that produces gametes.

Gametes are haploid (n) cells


10.1 Meiosis

Chapter 10

• When 2 gametes combine during fertilization, thenormal (2n) number of chromosomes is

restored.

Stages of Meiosis

Meiosis reduces the chromosome number (2n) to half (n) through the separation of homologous chromosomes

Human meiosis reduces the cell from 46 to 23 chromosomes.


Involves two consecutive cell divisions called Meiosis I and Meiosis II

10.1 Meiosis

Chapter 10

Meiosis I - Interphase


10.1 Meiosis

Chromosomes replicate.

Chromatin condenses.

Chapter 10

Interphase

Meiosis I – Prophase I


10.1 Meiosis

Pairing of homologous chromosomes occurs.(called synapsis)

Each chromosome consists of two chromatids.

The nuclear envelope breaks down.

Spindles form.

Chapter 10

Prophase I

Meiosis I – Prophase I Cont’d


10.1 Meiosis

During Prophase I, crossing over creates genetic variation.

Crossing over—chromosomal segments are exchanged between a pair of homologous chromosomes.

Chapter 10

Meiosis I – Metaphase I


10.1 Meiosis

Chromosome centromeres attach to spindle fibers.

Homologous chromosomes line up at the equator.

Chapter 10

Metaphase I

Meiosis I – Anaphase I


10.1 Meiosis

Chapter 10

Anaphase I

Entire homologous chromosomes separate and moveto opposite poles of the cell.

Meiosis I – Telophase I


10.1 Meiosis

The spindles break down.

Chromosomes uncoil and form two nuclei.

The cell divides.

There is no interphase following Meiosis I

Chapter 10

Telophase I

Meiosis II – Prophase II


10.1 Meiosis

Chapter 10

A second set of phases beginsas the spindle apparatus forms and the chromosomes condense.

Meiosis II is like mitosis.

Prophase II

Meiosis II – Metaphase II


10.1 Meiosis

Chapter 10

A haploid number of chromosomesline up at the equator.

Metaphase II

Meiosis II – Anaphase II


10.1 Meiosis

Chapter 10

Anaphase II

The sister chromatids arepulled apart at the centromere by spindle fibers and move toward the opposite poles of the cell.


10.1 Meiosis

Meiosis II – Telophase II

Chapter 10

The chromosomes reach the poles, andthe nuclear membrane and nuclei reform.

Telophase II

Meiosis II - Cytokinesis


Cytokinesis results in four haploid cells, each with n number of chromosomes.

The 4 daughter cells are genetically unique.

10.1 Meiosis

Chapter 10

Cytokinesis

The Importance of Meiosis

Meiosis consists of two sets of divisions


Produces four haploid daughter cells that are not identical

10.1 Meiosis

Results in genetic variation

Chapter 10

Other Concepts in Sexual Reproduction

Fertilization - the joining of a sperm & egg to form a fertilized egg cell called a zygote.


Pollination in Plants

- when pollen grains (sperm cells) from a seed plant land on the female reproductive structure of the plant. This leads to fertilization & seed formation.

This process is aided by wind & animals


Conjugation

- A process in which two cells (prokaryotic or protist) connect to each other and exchange genetic information – thereby increasing genetic variation.


Sexual vs. Asexual Reproduction

Asexual reproduction The organism inherits all of its chromosomes

from a single parent. The new individual is genetically identical

to its parent.

10.1 Meiosis

Chapter 10

Advantages: Doesn’t require a partner, faster,works well in a stable environment.

Disadvantages: No genetic variation. A majorenvironmental change can wipe out a species.


Sexual vs. Asexual Reproduction

Sexual reproduction The organism inherits different genetic info

from each parent. The new individual is genetically unique

from its parents.

10.1 Meiosis

Chapter 10

Advantages: More genetic variation meanspossible survival in a changing environment.

Disadvantages: Slower, 2 parents & mating required.

1. A2. B3. C4. D

FQ 7

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Sexual Reproduction and GeneticsChapter 10

10.2 Formative Questions

In rabbits, gray fur (G) is dominant to black fur (g). If a heterozygous male is crossed with a heterozygous female, what is the phenotypic ratio of the possible offspring?

A. 1:1

B. 1:2:1

C. 2:1

D. 3:1

1. A2. B3. C4. D

FQ 8

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Which explains how the shuffling of genes during meiosis results in billions of possible combinations?

A. crossing over

B. gene linkage

C. genetic recombination

D. independent segregation


1. A

2. B

FQ 9



Two genes on the same chromosome may become separated during meiosis.

A. true

B. false

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1. A2. B3. C4. D

FQ 10

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What is the term for an organism that has one or more sets of extra chromosomes in its cells?

A. diploid

B. gamete

C. hybrid

D. polyploid

1. A2. B3. C4. D

CAQ 1

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A. 6

B. 12

C. 24

D. 36

How many chromosomes would a cell have during metaphase I of meiosis if it has 12 chromosomes during interphase?

Chapter Assessment Questions

1. A2. B3. C4. D

CAQ 2

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A. prophase I

B. interphase

C. anaphase I

D. anaphase II

Which stage of meiosis is illustrated?

1. A2. B3. C4. D

CAQ 3

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What is the next step for the chromosomes illustrated?

A. Chromosomes replicate.

B. Chromosomes move to opposite poles.

C. Chromosomes uncoil and form two nuclei.

D. Chromosomes line up at the equator.

1. A2. B3. C4. D

Standardized Test Practice

STP 1

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What is this process called?

A. fertilization

B. gamete formation

C. inheritance

D. reproduction

1. A2. B3. C4. D


STP 2

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Before meiosis I, the sister chromatids of this chromosome were identical. What process caused a change in a section of one chromatid?

A. DNA replication

B. crossing over

C. synapsis

D. telophase

1. A2. B3. C4. D


STP 3

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At what stage is the chromosome number reduced from 2n to n?

A. prophase I

B. metaphase I

C. anaphase I

D. meiosis II

1. A2. B3. C4. D


STP 4

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To which step in this process does the law of segregation apply?

A. grows into plant

B. gamete formation

C. fertilization

D. seed development

1. A2. B3. C4. D


STP 5

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For human eye color, brown is dominant and blue is recessive. If a husband is heterozygous and his wife has blue eyes, what is the probability that their child will have blue eyes?

A. 0

B. 1/4

C. 1/2

D. 1

state standard 2e. compare the advantages of sexual reproduction and asexual reproduction in...

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